1. Field of the Invention
The present invention relates to an apparatus and a method for controlling compressors of an air conditioner.
2. Description of the Related Art
Generally, an air conditioner is an appliance for cooling or heating a room such as a house, a restaurant, or an office. The air conditioner comprises a compressor, a condenser, an expansion device, an evaporator, and a refrigerant pipe. The compressor serves to compress a refrigerant into a high-temperature and high-pressure gaseous state. The condenser serves to condense the refrigerant passing through the compressor into a high-temperature and high-pressure liquid state. The expansion device serves to decompress the refrigerant passing through the condenser into a low-temperature and low-pressure liquid state. The evaporator serves to evaporate the refrigerant passing through the expansion device into a low-temperature and low-pressure gaseous state. The compressor, the condenser, the expansion device, and the evaporator are connected by the refrigerant pipe.
A heat pump-type air conditioner further comprises a direction change valve, such as a 3-way valve or a 4-way valve, adapted to change the flow direction of the refrigerant based on a cooling/heating purpose, thereby being selectively operated in a cooling or heating mode.
In the cooling mode of the air conditioner, an outdoor heat exchanger serves as the condenser, and an indoor heat exchanger serves as the evaporator. On the other hand, in the heating mode of the air conditioner, the outdoor heat exchanger serves as the evaporator, and the indoor heat exchanger serves as the condenser.
In the cooling mode, the air conditioner allows indoor air to pass through the indoor heat exchanger serving as the evaporator, thereby discharging cold air. In the heating mode, the air conditioner allows indoor air to pass through the indoor heat exchanger serving as the condenser, thereby discharging warm air.
Recent air conditioners have employed a plurality of compressors having different capacities so that the plural compressors are simultaneously or selectively operated in accordance with cooling or heating loads. Accordingly, it is possible to properly cope with the cooling or heating load, thereby optimizing the cooling or heating efficiency of the air conditioner.
In order to determine the refrigerant compression capacity of the compressors of the air conditioner, the cooling or heating load must be correctly measured. Generally, the load is determined by the difference between a room temperature and a target temperature (T0) designated by a user.
Herein, an upper limit target temperature (T0+) and a lower limit target temperature (T0xe2x88x92) of the target temperature (T0) are set by an allowable temperature deviation. When the room temperature (T) deviates from the range of the target temperature (T0), a plurality of the compressors are simultaneously operated or stopped, or partially operated or stopped.
FIG. 1 is a graph depicting a variation in compression capacity of compressors depending on a variation in room temperature in a conventional air conditioner employing plural compressors.
With reference to FIG. 1, when the air conditioner is operated in a heating mode, the variation in room temperature is described. When the room temperature (T) is increased and reaches the upper limit target temperature (T0+) by the operation of the air conditioner in the heating mode, the compressors of the air conditioner are stopped. When the room temperature (T) is decreased and becomes lower than the lower limit target temperature (T0xe2x88x92), the compressors of the air conditioner are re-operated.
Here, when the compressors of the air conditioner are initially operated, the room temperature (T) is gradually increased to the upper limit target temperature (T0+) at an initial stage of the heating mode. However, when the compressors of the air conditioner are re-operated, the room temperature is relatively rapidly increased to the upper limit target temperature (T0+).
It is concluded that the load to be eliminated by the re-operations of the compressors is smaller than the load to be eliminated by the initial operations of the compressors under the same room temperature.
The reason is that the load is substantially affected by various external factors such as latent heat in the room air.
As aforementioned, the conventional air conditioner cannot correctly determine the load only by means of the difference between the room temperature (T) and the target temperature (T0), thus not being capable of rapidly eliminating the load. Further, a plurality of the compressors of the conventional air conditioner are unnecessarily operated or stopped simultaneously, thereby degrading the operational reliability of the compressors.
Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide an apparatus for controlling compressors of an air conditioner, which correctly determines loads, thereafter effectively operating the plural compressors, thereby rapidly eliminating the loads and preventing the unnecessary operations of the compressors.
It is another object of the present invention to provide to a method for controlling compressors of an air conditioner, which correctly determines loads based on room temperature, target temperature, and a variation in the room temperature, thereby effectively operating the plural compressors.
In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of an apparatus for controlling a plurality of compressors of an air conditioner, comprising: a counter for counting the number of times of operations/stoppages of the plural compressors according to loads; a timer for sensing a time (t) taken for the plural compressors to be operated/stopped a designated number of times counted by the counter; and a controller for controlling the operations of the plural compressors based on the time (t) sensed by the timer.
Preferably, the timer may sense the time (t) taken for the plural compressors to be operated/stopped two times.
Further, preferably, the controller may include a comparison unit for comparing the time (t) sensed by the timer to a designated time (t0), thereby determining whether the load is eliminated.
Preferably, the timer may be reset when a control signal regarding the time (t) sensed by the timer is transmitted to the controlling unit, and the counter may be reset when the timer is reset.
Further, preferably, the comparison unit may determine the load to be eliminated when the time (t) sensed by the timer is not more than the designated time (t0), and may determine the load not to be eliminated when the time (t) sensed by the timer is more than the designated time (t0).
Moreover, preferably, the controller may operate a part of the plural compressors when it is determined that the load is eliminated, and may operate all of the plural compressors when it is determined that the load is not eliminated.
In accordance with another aspect of the present invention, there is provided a method for controlling a plurality of compressors of an air conditioner, comprising the steps of: (a) repeating operations/stoppages of the plural compressors according to loads; (b) sensing a time (t) taken for the plural compressors to be operated/stopped a designated number (n) of times at the step (a); (c) determining whether or not the load is eliminated based on the time (t) sensed at the step (b); and (d) selectively operating a part of the plural compressors when it is determined that the load is eliminated from the result obtained by the step (c).
Preferably, the time (t) sensed at the step (b) may be taken for the plural compressors to be operated/stopped two times.
Further, preferably, the step (c) may include the steps of: (c-1) determining the load to be eliminated when the sensed time (t) is not more than a designated time (to); and (c-2) determining the load not to be eliminated when the sensed time (t) is more than the designated time (to)
Preferably, the step (c) may include the step of (c-3) being reset based on a result obtained by comparing the sensed time (t) to a designated time (to)
Moreover, preferably, the step (d) may include the steps of (d-1) operating/stopping the plural compressors the designated number (n) of times at the step (b) when it is determined that the load is not eliminated at the step (c).